Biaxially oriented nylon film, laminate wrapping material and process for production of biaxially oriented nylon film

ABSTRACT

Biaxially-oriented nylon film according to the present invention is biaxially-oriented nylon film made from nylon. In the biaxially-oriented nylon film, an elongation ratio of the film in each of four directions (an MD direction, a TD direction, a 45 degree direction and a 135 degree direction) until a film rupture is 70 percent or more, the elongation ratio being measured in a tensile test (testing conditions: a sample width is 15 mm; a distance between gauge points is 50 mm; and a tensile speed is 100 mm/min), and a stress ratio A (σ 1 /σ 2 ) between a tensile stress σ 1  and a tensile stress σ 2  in a stress-strain curve obtained in the tensile test of the film is 2 or more in each of the four directions, the tensile stress σ 1  being a value at a point where the elongation ratio becomes 50 percent while the tensile stress σ 2  being a value at an yield point.

TECHNICAL FIELD

The present invention relates to biaxially-oriented nylon film, alaminated packing material and a manufacturing method for thebiaxially-oriented nylon film.

BACKGROUND ART

Biaxially-oriented nylon film (hereinafter also referred to as ONyfilm), which is excellent in strength, impact resistance andanti-pinhole property, is frequently used for packaging a product suchas a heavy product or liquid product on which a great load is applied.

There has been conventionally known a technique to use nylon for apacking material used in such a forming as a deep-drawing, a stretchforming or the like (see e.g. Patent Document 1, Patent Document 2).

Specifically, Patent Document 1 discloses resin sheet for cold formingthat includes: a base material layer that contains a polystyrene-basedresin; and a functional layer that is single-layered or two-layered onboth surfaces or one surface of the base material layer. In addition,according to Patent Document 1, as the functional layer, an abrasionresistance layer that contains a nylon resin is provided on an exteriorlayer of the resin sheet for cold forming.

According to such resin sheet for cold forming, a cool-formed articlethat is excellent in impact resistance and shape-retaining property canbe obtained. By providing the abrasion resistance layer containing thenylon resin on the exterior layer of the sheet, the exterior layer ofthe sheet can be prevented from being damaged during cool-forming.

As described in Patent Document 1, as compared with hot-forming,cool-forming is excellent in that a size of an apparatus can be reducedwith a heater being omitted and that a continuous forming at high speedcan be realized.

On the other hand, Patent Document 2 discloses composite sheet fordeep-drawing that is formed by laminating plural pieces of sheet thatincludes a seal layer, a middle layer and an outer layer. In the sheet,the seal layer includes a polypropylene-based resin layer, the middlelayer includes an oxygen-barrier resin layer, a nylon-based resin layerand a polyethylene-based resin layer, and the outer layer is made from ahygroscopic material.

According to such composite sheet for deep-drawing, the composite sheetcan be given a mechanical strength by providing the nylon-based resinlayer in the middle layer. With this arrangement, an occurrence of apinhole during deep-drawing at approximately 150 degrees C. can beprevented.

-   [Patent Document 1] JP-A-2004-74795-   [Patent Document 2] JP-A-2004-98600

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, since there is no detailed description in Patent Document 1with respect to the nylon-based resin layer provided on the exteriorlayer of the resin sheet for cold-forming, the resin sheet may not showa favorable formability, strength or anti-pinhole property forcold-forming, depending on the nylon resin layer used therein. In such acase, a molded article of a sharp shape may not be obtained, and apinhole may be formed in the sheet during cool-forming.

In Patent Document 2, although there is a detailed description withrespect to a material used for forming the nylon-based resin layer,there is no detailed description with respect to mechanical propertysuch as an elongation ratio of the nylon-based resin layer. In addition,although referring to deep-forming at approximately 150 degrees C.,Patent Document 2 does not refer to cool-forming. Accordingly, as inPatent Document 1, a favorable molded article may not be obtained bycool-forming.

An object of the present invention is to provide, as a main basematerial for packing material used in cool-forming etc.,biaxially-oriented nylon film that is excellent in formability, strengthand anti-pinhole property, a laminated packing material including thesame and a manufacturing method of the biaxially-oriented nylon film.

Means for Solving the Problems

According to a finding on which the present invention is based,biaxially-oriented nylon film (ONy film) that is excellent informability, strength and anti-pinhole property can be obtained whenpredetermined conditions are satisfied with respect to an elongationratio until a rupture in each four directions (an MD direction, a TDdirection, a 45 degrees direction and a 135 degrees direction) obtainedin a tensile test of the ONy film and to a tensile stress σ₁ at a pointwhere the elongation ratio becomes 50 percent and tensile stress σ₂ atan yield point in a stress-strain curve obtained in the tensile test ofthe film.

In short, according to the present invention, biaxially-oriented nylonfilm described as follows is provided.

Biaxially-oriented nylon film according to an aspect of the presentinvention is biaxially-oriented nylon film made from nylon 6, in whichan elongation ratio of the film in each of four directions (an MDdirection, a TD direction, a 45 degree direction and a 135 degreedirection) until a film rupture is 70 percent or more, the elongationratio being measured in a tensile test (testing conditions: a samplewidth is 15 mm; a distance between gauge points is 50 mm; and a tensilespeed is 100 mm/min), and a stress ratio A (σ₁/σ₂) between a tensilestress σ₁ and a tensile stress σ₂ in a stress-strain curve obtained inthe tensile test of the film is 2 or more in each of the fourdirections, the tensile stress σ₁ being a value at a point where theelongation ratio becomes 50 percent while the tensile stress σ₂ being avalue at an yield point.

According to the aspect of the present invention, since the elongationratio until the rupture in each of the four directions obtained in thetensile test of the ONy film is 70 percent or more and the stress ratioA in the stress-strain curve of the ONy film is 2 or more in each of thedirections, the ONy film is excellent in formability, strength andanti-pinhole property, which is specifically favorable in cold-forming.According to a laminated packing material formed to contain such ONyfilm, no pinhole is formed in the ONy film during cold deep-drawing orthe like, thereby manufacturing a molded article of a sharp shape.

In the present invention, cold-forming refers to forming that isconducted under an atmosphere at a temperature less than a glasstransition point (Tg) of a resin. Preferably in cool-forming, using acool-forming machine for forming aluminum foil, a sheet material isforced into a female die by a male die to be pressed at high speed. Inthis manner, without being heated, the sheet material can experiencesuch a plastic deformation as molding, bending, shearing and drawing.

In the biaxially-oriented nylon film according to the aspect of thepresent invention, it is preferable that a crystallinity degree of thefilm is in a range of 20 to 38 percent.

According to the aspect of the present invention, since thecrystallinity is in the range of 20 to 38 percent, the film exhibits afavorable elongation property during forming.

In the biaxially-oriented nylon film according to the aspect of thepresent invention, it is preferable that the film is made from a filmforming material that contains a virgin material and a thermalhysteresis material, the virgin material being formed of nylon 6(hereinafter also referred to as Ny6) and metaxylylene adipamide(hereinafter also referred to as MXD6), the thermal hysteresis materialbeing obtained by melt-kneading Ny6 and MXD6 and by setting the MXD6 tohave a melt point of 233 to 238 degrees C., and a hydrothermal shrinkagefactor of the film is 3 to 20 percent in each of the MD direction andthe TD direction of the film when the film is retained in hot liquid of95 degrees C. for thirty minutes.

According to the aspect of the present invention, since the hydrothermalshrinkage factor of the film when the film is retained in the hot liquidof 95 degrees C. for thirty minutes is in the range of 3 to 20 percent,the film exhibits a favorable elongation property during forming.

According to a laminated packing material formed to contain such ONyfilm, since MXD6 is contained in the ONy film, the laminated packingmaterial exhibits an excellent heat resistance. Accordingly, when thepacking material having been formed by laminating an ONy film layer anda sealant layer is heated by a seal bar to be seal-treated, the packingmaterial does not adhere to the seal bar, whereby a favorableseal-treatment can be realized. Further, according to the packingmaterial, since the ONy film layer contains the thermal hysteresismaterial, an occurrence of an intra-layer separation inside the ONy filmlayer can be prevented, whereby a molded article that is excellent inimpact resistance can be obtained.

In the biaxially-oriented nylon film according to the aspect of thepresent invention, it is preferable that the Ny6 and the MXD6 arecontained in the virgin material by ratios of 60 to 85 parts by mass and15 to 40 parts by mass respectively, and a content of the thermalhysteresis material is 5 to 40 percent by mass of the total amount ofthe film forming material.

In the biaxially-oriented nylon film according to the aspect of thepresent invention, it is preferable that the Ny6 and the MXD6 arecontained in the thermal hysteresis material by ratios of 60 to 85 partsby mass and 15 to 40 parts by mass respectively.

In the biaxially-oriented nylon film according to the aspect of thepresent invention, it is preferable that a ratio (A_(max)/A_(min))between a maximum stress ratio A_(max) and a minimum stress ratioA_(min) of the stress ratios A obtained with respect to the fourdirections is 2 or less.

In the biaxially-oriented nylon film according to the aspect of thepresent invention, it is preferable that a tensile-rupture strength ofthe film in each of the four directions measured in the tensile test ofthe film is 180 MPa or more.

A laminated packing material according to another aspect of the presentinvention is a laminated packing material that includes theabove-described biaxially-oriented nylon film.

A method of manufacturing biaxially-oriented nylon film according tostill further aspect of the present invention is a manufacturing methodof biaxially-oriented nylon film made from nylon 6, the method includingsteps of: biaxially-orienting unoriented raw film made from the nylon 6under a condition where an oriented ratio of the film in each of an MDdirection and a TD direction becomes 2.8 times or more; andheat-treating the raw film at a temperature between 205 and 215 degreesC. to manufacture biaxially-oriented nylon film, in which an elongationratio of the film in each of four directions (the MD direction, the TDdirection, a 45 degree direction and a 135 degree direction) until afilm rupture is 70 percent or more, the elongation ratio being measuredin a tensile test (testing conditions: a sample width is 15 mm; adistance between gauge points is 50 mm; and a tensile speed is 100mm/min), and a stress ratio A (σ₁/σ₂) of a tensile stress σ₁ and atensile stress σ₂ in a stress-strain curve obtained in the tensile testof the film is 2 or more in each of the four directions, the tensilestress σ₁ being a value at a point where the elongation ratio becomes 50percent while the tensile stress σ₂ being a value at an yield point.

A method of manufacturing biaxially-oriented nylon film according tostill further aspect of the present invention is a manufacturing methodof biaxially-oriented nylon film made from a film forming material thatcontains nylon 6, the method including steps of: biaxially-orientingunoriented raw film made from the nylon 6 under a condition where anoriented ratio of the film in each of an MD direction (a direction inwhich the film is moved) and a TD direction (a direction of a filmwidth) becomes 2.8 times or more; and heat-treating the raw film at atemperature between 160 and 200 degrees C. to manufacturebiaxially-oriented nylon film, in which a crystallinity degree of thefilm is in a range of 20 to 38 percent, an elongation ratio of the filmin each of four directions (the MD direction, the TD direction, a 45degree direction and a 135 degree direction) until a film rupture is 70percent or more, the elongation ratio being measured in a tensile test(testing conditions: a sample width is 15 mm; a distance between gaugepoints is 50 mm; and a tensile speed is 100 mm/min), and a stress ratioA (σ₁/σ₂) of a tensile stress σ₁ and a tensile stress σ₂ in astress-strain curve obtained in the tensile test of the film is 2 ormore in each of the four directions, the tensile stress σ₁ being a valueat a point where the elongation ratio becomes 50 percent while thetensile stress σ₂ being a value at an yield point.

A method of manufacturing biaxially-oriented nylon film according tostill further aspect of the present invention is a manufacturing methodof biaxially-oriented nylon film made from a film forming material thatcontains a virgin material and a thermal hysteresis material, the virginmaterial being formed of Ny6 and MXD6, the thermal hysteresis materialbeing obtained by melt-kneading Ny6 and MXD6 and by setting the MXD6 tohave a melt point of 233 to 238 degrees C., the method including stepsof: biaxially-orienting unoriented raw film made from the nylon 6 undera condition where an oriented ratio of the film in each of an MDdirection (a direction in which the film is moved) and a TD direction (adirection of a film width) becomes 2.8 times or more; and heat-treatingthe raw film at a temperature between 160 and 200 degrees C. tomanufacture biaxially-oriented nylon film, in which a hydrothermalshrinkage factor of the film is 3 to 20 percent in each of the MDdirection and the TD direction of the film when the film is retained inhot liquid of 95 degrees C. for thirty minutes, an elongation ratio ofthe film in each of four directions (the MD direction, the TD direction,a 45 degree direction and a 135 degree direction) until a film ruptureis 70 percent or more, the elongation ratio being measured in a tensiletest (testing conditions: a sample width is 15 mm; a distance betweengauge points is 50 mm; and a tensile speed is 100 mm/min), and a stressratio A (σ₁/σ₂) of a tensile stress σ₁ and a tensile stress σ₂ in astress-strain curve obtained in the tensile test of the film is 2 ormore in each of the four directions, the tensile stress σ₁ being a valueat a point where the elongation ratio becomes 50 percent while thetensile stress σ₂ being a value at an yield point.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph showing an example of a stress-strain curve obtainedwhen a tensile test is conducted on ONy film according to a first andthird embodiments of the present invention; and

FIG. 2 is an illustration schematically showing a biaxially-orientingapparatus for manufacturing the ONy film according to the first andthird embodiments of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

A first embodiment of the present invention will be described in detailbelow.

[Arrangement of Biaxially-Oriented Nylon Film]

Biaxially-oriented nylon film (ONy film) according to the presentembodiment is formed by biaxially-orienting unoriented raw film madefrom nylon 6 (hereinafter called, Ny6) and heat-treating the orientedraw film at a predetermined temperature. By biaxially-orienting theunoriented raw film as described above, ONy film excellent in impactresistance can be obtained.

The chemical formula of the Ny6 is represented by Formula 1 below.H—[NH—(CH₂)₅—CO]n-OH

In the present embodiment, an elongation ratio, a stress ratio A and atensile-rupture stress of the ONy film in each four directions (MDdirection, TD direction, 45 degree direction and 135 degree direction)until a tensile rupture of the film are obtained based on astress-strain curve obtained through a tensile test (a sample width of15 mm, a distance between gauges points of 50 mm and a tensile speed of100 mm/min) conducted on the ONy film.

An example of the stress-strain curve obtained through the tensile testis shown in FIG. 1.

In FIG. 1, the vertical scale shows a tensile stress σ (MPa) of the ONyfilm while the horizontal scale shows a strain ε of the ONy film(ε=Δl/l, in which l represents an initial length of the film and Δlrepresents an increment in the film length). By conducting the tensiletest on the ONy film, the tensile stress σ is increased in such a manneras to substantially satisfy a direct function in accordance with anincrease in the strain ε, such that an increasing trend of the tensile σat a predetermined strain ε₁ is greatly changed. In the presentembodiment, the point (ε₁, σ₂) is defined as an yield point. When thestrain ε is further increased, the tensile stress σ is also increasedaccordingly. When the strain c is increased up to a predetermined strainε₂, the film is ruptured. Stress-strain curves correspondingrespectively to the four directions (MD direction, TD direction, 45degrees direction and 135 degrees direction) are obtained per one pieceof the ONy film.

In the ONy film according to the present embodiment, the elongationratios in the four directions (the MD direction, the TD direction, the45 degrees direction and the 135 degrees direction) until the filmrupture in the tensile test are required to be 70 percent or more. Inother words, as in the stress-strain curve shown in FIG. 1, the strainε₂ at the time of the film rupture is required to be 0.7 or more. Withthis arrangement, the ONy film can be stretched in a balanced manner,thereby improving a drawing-formability of the ONy film when the ONyfilm is formed to be a laminate material. When the elongation ratio inone of the four directions is less than 70 percent, the film can beeasily ruptured in a cold deep-drawing operation, whereby a goodformability is not obtained.

It is more preferable that a value obtained by dividing a maximumelongation ratio by a minimum elongation ratio out of the elongationratios in the four directions is 2.0 or less. With this arrangement, theONy film can be stretched in a further balanced manner.

In addition, it is preferable that the elongation ratios of the ONy filmin the four directions are 75 percent or more and that the valueobtained by dividing the maximum elongation ratio by the minimumelongation ratio out of the elongations ratios in the four directions is2.0 or less, whereby a further excellent formability can be obtained.

In the ONy film according to the present embodiment, a stress ratio A(σ₁/σ₂) between the tensile stress σ₁ when the elongation ratio becomes50 percent (strain ε=0.5) and the tensile stress σ₂ at the yield pointin the stress-strain curve exemplarily shown in FIG. 1 is required to be2 or more (more preferably 2.2 or more) in each of the four directions.With this arrangement, a formation of a pinhole during the colddeep-drawing operation can be reliably prevented, whereby a moldedarticle of a sharp shape can be manufactured. When the stress ratio A isless than 2 in one of the directions, a film thickness may be unevenwith the film being partially thinned, whereby the film may be ruptured.

A ratio (A_(max)/A_(min)) between a maximum stress ratio A_(max) and aminimum stress ratio A_(min) out of the stress ratios A in the fourdirections is preferably 2.0 or less (more preferably 1.8 or less). Withthis arrangement, the film can be stretched in a balanced manner duringa cold forming operation, whereby a molded article with a uniformthickness can be manufactured. When the ratio A_(max)/A_(min) is morethan 2.0, the film thickness may be uneven with the film being partiallythinned, whereby the film may be ruptured.

Further, in the ONy film according to the present embodiment, atensile-rupture strength (σ₃) in each of the four directions ispreferably 180 MPa or more in the stress-strain curve exemplarily shownin FIG. 1. With this arrangement, a sufficient processing strength canbe obtained, whereby the ONy film can be more invulnerable to rupture inthe cold deep-forming operation or the like. At this time, a valueobtained by dividing a maximum strength by a minimum strength out of thetensile-rupture strengths in the four directions is preferably 2.0 orless, whereby a well-balanced processing strength can be obtained.

It is preferable that the tensile-rupture strengths of the ONy film inthe four directions are 200 MPa or more and that the value obtained bydividing the maximum strength by the minimum strength out of thetensile-rupture strengths in the four directions is preferably 1.8 orless, whereby a better-balanced processing strength can be obtained.

[Manufacturing Method of ONy Film]

The above-described ONy film can be obtained by biaxially-orienting theunoriented raw film made from Ny6 under a condition where an orientedratio in each of the MD direction and the TD direction becomes 2.8 timesor more and by heat-treating the oriented raw film at a temperaturesbetween 205 and 215 degrees C.

As a method of biaxial orienting, a simultaneous biaxial-orienting or asequential biaxial-orienting such as a tubular method or a tenter methodcan be employed. However, in light of a strength balance between alengthwise direction and a widthwise direction, it is preferable toperform the simultaneous biaxial-orienting according to the tubularmethod.

Specifically, the ONy film according to the present embodiment can bemanufactured as follows.

After Ny6 pellets are melt-kneaded in an extruder at 270 degrees C., amolten material is extruded from a die in a shape of cylindrical film.By subsequently quenching the extruded molten material by water, a rawfilm is prepared.

Then, as exemplarily shown in FIG. 2, after inserted between a pair ofnip rollers 12, the raw film 11 is heated by a heater 13 while a gas isinjected into the raw film 11. The raw film 11 is applied with air 15from an air ring 14 at a drawing start point to be distended to form abubble 16. By pulling the raw film 11 using a pair of nip rollers 17provided at a downstream side, the simultaneous biaxial orienting in theMD direction and the TD direction according to the tubular method isperformed. At this time, the oriented ratio in each of the MD directionand the TD direction is required to be 2.8 times or more. When theoriented ratio is less than 2.8 times, an impact strength isdeteriorated, which is practically unfavorable.

Subsequently, the oriented film is put into a tenter heat treat furnace(not shown) to be heat-fixed at 205 to 215 degrees C., whereby ONy film18 according to the present embodiment is obtained. When a heat-treatingtemperature is higher than 215 degrees C., due to an excessive growth ofa bowing phenomenon, an anisotropy in a width direction is increasedwhile a crystallinity degree is excessively increased, whereby thestrength is deteriorated. On the other hand, when the heat-treatingtemperature is lower than 205 degrees C., due to an excessive increasein a film shrinkage factor, the film may be easily shrunk during asecondary processing.

[Arrangement of Laminated Packing Material]

A laminated packing material according to the present embodiment isformed by laminating onto at least one surface of the ONy film anotherlaminate base material of one layer or of two layers or more.Specifically, the other laminate base material may be exemplarily a filmthat includes an aluminum layer or the like.

Generally, a laminated packing material including the aluminum layer isnot suitable for cool forming because the aluminum layer can be easilyruptured due to necking during a cool forming operation. In this regard,in the laminated packing material according to the present embodiment,since the ONy film is excellent in a formability, impact resistance andanti-pinhole property, the aluminum layer can be prevented from beingruptured during a cool stretch-expanding operation or a cooldeep-drawing operation, thereby preventing a pinhole formation in thepacking material. Accordingly, even when the total thickness of thepacking material is small, a molded article of a sharp shape with highstrength can be obtained.

The total thickness of the laminated packing material according to thepresent embodiment (i.e., a sum of thicknesses of the ONy film and theother laminate base material) is preferably 200 μm or less. When thetotal thickness is more than 200 μm, corner portions of the packingmaterial may not be easily formed by cool forming, whereby a moldedarticle of a sharp shape may not be obtained.

The thickness of the ONy film in the laminated packing materialaccording to the present embodiment is preferably 5 to 50 μm, morepreferably 10 μm to 30 μm. When the thickness of the ONy film is lessthan 5 μm, impact resistance of the laminated packing material may bedeteriorated, whereby a sufficient cool formability may not be obtained.On the other hand, when the thickness of the ONy film is more than 50μm, impact resistance of the laminated packing material may not befurther improved even though the total thickness of the packing materialis increased, which is unfavorable.

As the aluminum layer used in the laminated packing material accordingto the present embodiment, aluminum foil formed from pure aluminum orfrom a soft material of aluminum-iron alloy may be used. In order toimprove laminate property, the aluminum foil preferably experiences apretreatment such as an undercoating treatment by silane coupling agentor titanium coupling agent, a corona discharge treatment and the like,such that the pretreated aluminum foil is laminated onto the ONy film.

A thickness of the aluminum layer is preferably 20 to 100 μm. With thisarrangement, a shape of the molded article can be well-maintained, andoxygen, moisture and the like can be prevented from being permeatedthrough the packing material.

When the thickness of the aluminum layer is less than 20 μm, thealuminum layer may be easily ruptured during the cool forming of thelaminated packing material. Even when the aluminum layer is notruptured, a pinhole or the like may be easily formed. Thus, oxygen,moisture and the like may be permeated through the packing material. Onthe other hand, when the thickness of the aluminum layer is more than100 μm, neither the rupture during the cool forming nor a formation ofthe pinhole is notably prevented even though the total thickness of thepacking material is increased, which is unfavorable.

Second Embodiment

A second embodiment of the present invention will be described in detailbelow.

In the description of the second embodiment, what has been alreadydescribed in the preceding first embodiment will not be repeated.

[Arrangement of Biaxially-Oriented Nylon Film]

Biaxially-oriented nylon film (ONy film) according to the presentembodiment is formed by biaxially-orienting unoriented raw film madefrom a material containing Ny6 and heat-treating the oriented raw filmat a predetermined temperature, as in the first embodiment.

Unlike the first embodiment, the ONy film preferably has a crystallinitydegree of 20 to 38 percent, more preferably 24 to 36 percent. With thisarrangement, ONy film that is excellently stretchable during a formingoperation as compared with general ONy film can be obtained, whereby therupture of the ONy film and the formation of the pinhole can beprevented during, for example, the cool forming operation. When thecrystallinity degree of the film is less than 20 percent, there is noparticular difference in the stretchability during the forming operationbetween the ONy film and general ONy film. On the other hand, when thecrystallinity degree of the film is more than 38 percent, a cooldrawing-formability and an impact strength may be deteriorated.

[Manufacturing Method of ONy Film]

The ONy film according to the present embodiment can be obtained bybiaxially-orienting the unoriented raw film made from the materialcontaining Ny6 under the condition where the oriented ratio in each ofthe MD direction and the TD direction becomes 2.8 times or more and byheat-treating the oriented raw film, as in the first embodiment.

However, although the heat-treating is performed at the temperaturebetween 205 and 215 degrees C. in the first embodiment, theheat-treating is performed at a temperature between 160 and 200 degreesC. in the present embodiment.

Specifically, the oriented film is put into a tenter heat treat furnace(not shown) to be heat-fixed at 160 to 200 degrees C., whereby ONy film18 according to the present embodiment is obtained.

[Arrangement of Laminated Packing Material]

The laminated packing material according to the present embodiment isprepared in the same manner as in the first embodiment, a description ofwhich is omitted.

Third Embodiment

A third embodiment of the present invention will be described in detailbelow.

In the description of the third embodiment, what has been alreadydescribed in the preceding embodiments will not be repeated.

[Arrangement of Biaxially-Oriented Nylon Film]

Biaxially-oriented nylon film (ONy film) according to the presentembodiment is formed by biaxially-orienting unoriented raw film madefrom a material containing: a virgin material formed from Ny6 and MXD6;and a thermal hysteresis material formed by melt-kneading Ny6 and MXD6,and by heat-treating the oriented raw film at a predeterminedtemperature. By biaxially-orienting the unoriented raw film as describedabove, ONy film excellent in impact resistance can be obtained.

The chemical formula of the Ny6 is represented by Formula 2 below whilethe chemical formula of the MXD6 is represented by Formula 3 below.H—[NH—(CH₂)₅—CO]n-OH

The above-mentioned virgin material generally means a material otherthan a mixture material having a history where the Ny6 and the MXD6 havebeen mixed to be melt-kneaded. For instance, even when the Ny6 or theMXD6 in a material individually has a melt-kneading history (e.g., arecycled product), the material is the virgin material as long as theNy6 and the MXD6 are not mixed to be melt-kneaded.

In light of the impact strength and the heat resistance of the ONy film,the Ny6 and the MXD6 are preferably contained in the virgin material bya ratio of 60 to 85 parts by mass (Ny6):15 to 40 parts by mass (MXD6).When the MXD6 in the virgin material is less than 15 parts by mass, theheat resistance is deteriorated. Accordingly, when the laminated packingmaterial, in which suitable sealant film is laminated onto the ONy film,is seal-treated, the laminated packing material may adhere to a sealbar. On the other hand, when the MXD6 is more than 40 parts by mass, theimpact strength is so much deteriorated as to impair practicalusability.

The above-mentioned thermal hysteresis material means a materialcontaining Ny6 and MXD6, the material having passed through an extruder.In the present invention, as the MXD 6, MXD6 whose melt point ismaintained within a range of 233 to 238 degrees C. (preferably within arange of 235 to 237 degrees C.) is used, the melt point being measuredwith a differential scanning calorimetry (DSC). The thermal hysteresismaterial may be prepared by recycling the ONy film obtained in thepresent invention. Since the thermal hysteresis material serves as acompatible solubilizer that has an affinity for both the Ny6 and theMXD6, an intra-layer separation of the ONy film can be prevented byadding the thermal hysteresis material to the ONy film.

The intra-layer separation means a phenomenon where a separation isinduced inside the ONy film when the ONy film onto which suitablesealant film has been laminated is used under such severe conditions asin the cool forming. The mechanism of the intra-layer separation has notbeen completely specified. However, it is speculated that the Ny6 andthe MXD6 are layer-oriented in the ONy film and the intra-layerseparation occurs between layers.

The melt point of the MXD6 in the thermal hysteresis material means amelt point measured before the thermal hysteresis material ismelt-kneaded with the virgin material. When the melt point of the MXD6in the thermal hysteresis material is less than 233 degrees C., theimpact strength of the ONy film is deteriorated. When the melt point ofthe MXD6 in the thermal hysteresis material is 238 degrees C. or more,the intra-layer separation may not be favorably prevented.

A content of the thermal hysteresis material is preferably 5 to 40percent by mass of the total amount of the ONy film forming material.When the thermal hysteresis material is less than 5 percent by mass, theintra-layer separation can be easily induced when the ONy film is usedunder such severe conditions as in the cool forming after the ONy filmis formed into a laminated film. When the thermal hysteresis material ismore than 40 percent by mass, the impact strength of the ONy film may bedeteriorated.

In light of the impact strength and a prevention of the intra-layerseparation, the Ny6 and the MXD6 is preferably contained in the thermalhysteresis material by a ratio of 60 to 85 parts by mass (Ny6):15 to 40parts by mass (MXD6). When a content ratio of the MXD6 in the thermalhysteresis material is less than 15 parts by mass (i.e., a content ratioof the Ny6 is more than 85 parts by mass), the intra-layer separation ofthe ONy film may not be favorably prevented. When the content ratio ofthe MXD6 in the thermal hysteresis material is more than 40 parts bymass (i.e., the content ratio of the Ny6 is less than 60 parts by mass),the impact strength of the ONy film may be deteriorated.

The ONy film according to the present embodiment is required to have ahydrothermal shrinkage factor of 3 to 20 percent in the MD direction andthe TD direction of the film respectively (preferably 6 to 20 percent)when the film is retained in hot liquid of 95 degrees C. for thirtyminutes. With this arrangement, ONy film that is excellently stretchableduring the forming operation as compared with general ONy film can beobtained, whereby the rupture of the ONy film and the formation of thepinhole can be prevented during, for example, the cool formingoperation. When the hydrothermal shrinkage factor of the film is lessthan 3 percent, there is no particular difference in the stretchabilityduring the forming operation between the ONy film and general ONy film.On the other hand, when the hydrothermal shrinkage factor of the film ismore than 20 percent, a delamination may occur between the ONy film andthe other film layer when the other film layer is laminated to the ONyfilm to form the laminated packing material.

[Manufacturing Method of ONy Film]

The ONy film according to the present embodiment can be obtained bybiaxially orienting the unoriented raw film made from the materialcontaining the virgin material and the thermal hysteresis material by apredetermined mixture ratio under the condition where the oriented ratioin each of the MD direction and the TD direction becomes 2.8 times ormore and by heat-treating the oriented raw film at a temperature between160 and 200 degrees C. The virgin material and the thermal hysteresismaterial are made from the Ny6 and the MXD6.

As a method of biaxial orienting, a simultaneous biaxial-orienting or asequential biaxial-orienting such as a tubular method or a tenter methodcan be employed. However, in light of a strength balance between alengthwise direction and a widthwise direction, it is preferable toperform the simultaneous biaxial-orienting according to the tubularmethod.

In order to prepare the Ny6 and the MXD6 contained in the virginmaterial, it is preferable to use and dry-blend pelleted Ny6 andpelleted MXD6. In addition, it is preferable to use pelleted thermalhysteresis material. For example, the pellets may be prepared by cuttingthe biaxially-oriented nylon film obtained according to the presentembodiment into small pieces and compressing the cut film. With thisarrangement, the thermal hysteresis material can be favorablydry-blended with the Ny6 pellets and the MXD6 pellets.

Specifically, the ONy film according to the present embodiment can bemanufactured as follows.

After the Ny6 pellets, the MXD6 pellets and the pelleted thermalhysteresis material are melt-kneaded in an extruder at 270 degrees C., amolten material is extruded from a die in a shape of cylindrical film.The extruded molten material is subsequently quenched by water, wherebya raw film is obtained.

Then, as exemplarily shown in FIG. 2, after inserted between the pair ofnip rollers 12, the raw film 11 was heated by the heater 13 while a gaswas injected into the raw film 11. The raw film 11 was applied with theair 15 from the air ring 14 at the drawing start point to be distendedto form the bubble 16. By pulling the raw film 11 using the pair of niprollers 17 provided at the downstream side, the simultaneous biaxialorienting in the MD direction and the TD direction according to thetubular method was performed. At this time, the oriented ratio in eachof the MD direction and the TD direction is required to be 2.8 times ormore. When the oriented ratio is less than 2.8 time, an impact strengthis deteriorated, which is practically unfavorable.

Subsequently, the oriented film is put into a tenter heat treat furnace(not shown) to be heat-fixed at 160 to 200 degrees C., whereby ONy film18 according to the present embodiment is obtained.

[Arrangement of Laminated Packing Material]

The laminated packing material according to the present embodiment isprepared in the same manner as in the first embodiment, a description ofwhich is omitted.

However, the laminated packing material according to the presentinvention contains the MXD 6 in the ONy film layer as well as thecomponents of the laminated packing material according to the firstembodiment, thereby exhibiting an excellent heat resistance.Accordingly, when the packing material includes a sealant layer, thepacking material does not adhere to the seal bar when heated by the sealbar to be seal-treated, whereby a favorable seal-treatment is realized.

According to the packing material, since the ONy film layer contains thethermal hysteresis material, no intra-layer separation occurs inside theONy film layer during the cool forming operation, so that a moldedarticle that is excellent in impact resistance can be obtained.

<Modification>

Although the best arrangements etc. for implementing the presentinvention has been described in the first to third embodiments, thepresent invention is not limited thereto. In other words, while thepresent invention has been described with reference to the specificembodiments, various modifications may be made to the above describedembodiments by those of ordinary skill in the art without departing fromthe spirit and scope of the invention.

Therefore, the description that limits the materials, the layerarrangements and the like is only an example to make the inventioneasily understood, but is not intended to limit the invention, so thatthe invention includes the description using a name without a part of orall of the limitation on the material etc.

For example, although the tubular method is employed as the method ofbiaxial orienting in the first to third embodiments, the tenter methodmay be used. In addition, the method of orienting may be performed bythe simultaneous biaxial orienting or by the sequential biaxialorienting.

The ONy film may be added with any necessary additives as desired. Suchadditives exemplarily include an anti-blocking agent (such as inorganicfiller), a water repellant (such as ethylene-bis-stearate ester) or alubricant (such as calcium stearate).

Although the laminated packing material in which the aluminum layer etc.is laminated to the ONy film is exemplified in the above describedembodiments, the arrangement is not limited thereto. In the laminatedpacking material according to the present invention, various functionallayers such as a sealant layer, an antistatic layer, a print layer, abarrier layer, a reinforcing layer and the like may be laminated.

EXAMPLE

Next, the first to third embodiments will be described in detail byreference to examples and comparative examples. It should be noted thatthe present invention is not limited to or by the examples describedbelow.

Examples of First Embodiment Examples 1, 2 Manufacturing of OrientedFilm

After Ny6 pellets were melt-kneaded in an extruder at 270 degrees C., amolten material was extruded from a die in a shape of cylindrical film.The extruded molten material was subsequently quenched by water, wherebya raw film was obtained. As the Ny6, nylon 6 manufactured by UbeIndustries, Ltd. [UBE NYLON 1023FD (trade name), relative viscosity:ηr=3.6] was used.

Then, as shown in FIG. 2, after inserted between the pair of nip rollers12, the raw film 11 was heated by the heater 13 while a gas was injectedinto the raw film 11. The raw film 11 was applied with the air 15 fromthe air ring 14 at the drawing start point to be distended to form thebubble 16. By pulling the raw film 11 using the pair of nip rollers 17provided at the downstream side, the simultaneous biaxial orienting inthe MD direction and the TD direction according to the tubular methodwas performed. The oriented ratios at the time of the orienting wererespectively 3.0 times (in the MD direction) and 3.2 times (in the TDdirection).

Subsequently, the oriented film was put into a tenter heat treat furnace(not shown) and heat-fixed at 210 degrees C., whereby ONy film 18(hereinafter, also referred to as ONy film 18) according to the presentexamples was obtained. The ONy film was 15 μm thick in Example 1 whilethe ONy film was 25 μm thick in Example 2.

[Evaluation Method]

(Tensile Test)

A tensile test of the ONy film 18 was conducted with a testermanufactured by Instron Corporation (Tester Type: 5564) underconditions: a sample with of 15 mm; a distance between fasteners of 50mm; and a tensile speed of 100 mm/min. Measurements were conducted onthe ONy film 18 with respect to the MD direction, the TD direction, the45 degrees direction and the 135 degrees direction. Based on thestress-strain curves obtained with respect to the directions of the ONyfilm, respective rupture elongation ratios (percent) in the directions,a ratio between a maximum value and a minimum value of the ruptureelongation ratios, the respective stress ratios A in the directions(A=σ₁/σ₂, in which σ₁ represents a tensile stress when the elongationrate is 50 percent while σ₂ represents a tensile stress at the yieldpoint) and the ratio between the maximum value A_(max) and the minimumvalue A_(min) of the stress ratios A were obtained.

(Drawing Formability)

Drawing formability of the laminated packing material including the ONyfilm 18 was evaluated.

Specifically, the laminated packing material was prepared by: using theONy film 18 according to each of Examples 1 and 2 as a front basematerial film; using L-LDPE film (UNILAX LS-711C (trade name),manufactured by Idemitsu Unitech CO., LTD, thickness of 120 μm) as asealant film; and dry-laminating the ONy film 18 and the L-LDPE film. Asan adhesive for dry-laminating, a blend of TAKELAC A-615 and TAKENATEA-65 (both of which are manufactured by Mitsui Takeda Chemicals, Inc.)was used (blend ratio: 16/1). The laminated packing material after thefilms were dry-laminated experienced an aging treatment at 40 degrees C.for three days.

The laminated packing materials manufactured as described aboveexperienced a cold deep-drawing (at a normal temperature), in which arectangular die in plan view (5 mm-by-10 mm) was used. Each of thelaminated packing materials experienced the deep-drawing ten times, andthe number of occurrences of a defect such as a pinhole, a crack and thelike was examined. When no defect occurred in any of ten timesdeep-drawing, the laminated packing material was rated as A. When such adefect occurred one to two times out of ten times, the laminated packingmaterial was rated as B, when three to five times, rated as C, and whensix times or more, rated as D.

(Piercing Strength)

A measurement of a piercing strength was conducted by: piercing the ONyfilm 18 with a needle of 1 mmφ at a piercing speed of 200 mm/min; andmeasuring a strength (N) required for the needle to pierce the film.

(Impact Strength)

A measurement of an impact strength was conducted with a film impacttester (manufactured by Toyo Seiki Seisaku-sho, Ltd.) by: striking fixedONy film 18 of a ring shape with a semispherical pendulum (diameter of ½inch); and measuring an impact strength (kg/cm) required for punchingthe film. Incidentally, the impact strength is represented in absolutevalue. The larger the value is, the more excellent impact resistance ofthe film is evaluated to be.

Comparative Example 1

After the Ny6 pellets were melt-kneaded in the extruder at 270 degreesC., the molten material was extruded from T-die. The extruded moltenmaterial was subsequently contact-cooled by a chill roller, wherebyunoriented raw film was manufactured. Incidentally, as the extruder, asingle-screwed extruder of 50 mmφ was used.

Next, the unoriented raw film was stretched to three times the originalsize in the MD direction while being heated at 100 degrees C. by aheating roller of a stretching device (compact biaxial stretchingdevice, manufactured by Nikkou Seisaku-sho Corporation). Immediatelythereafter, the unoriented raw film was stretched to 3.2 times theoriginal size in the TD direction with both ends thereof being graspedby a tenter device.

Then, the oriented film was put into a tenter heat treat furnace (notshown) and heat-fixed at 210 degrees C., whereby Ny film that wasbiaxially stretched in a sequential manner (thickness: 15 μm) accordingto Comparative Example 1 was obtained.

Comparative Example 2

After the Ny6 pellets were melt-kneaded in the extruder at 270 degreesC., the molten material was extruded from T-die. The extruded moltenmaterial was subsequently contact-cooled by a chill roller, wherebyunoriented raw film was manufactured. Incidentally, as the extruder, asingle-screwed extruder of 50 mmφ was used.

Then, using a biaxially stretching device (manufactured by NikkouSeisaku-sho Corporation), the unoriented raw film was stretched to 3.0times the original size both in the MD and TD directions while beingheated at 120 degrees C.

Additionally, the oriented film was heat-fixed by an oven at 210 degreesC., whereby Ny film that was biaxially stretched in a simultaneousmanner (thickness: 15 μm) according to Comparative Example 2 wasobtained.

The same evaluation test was conducted on Comparative Examples 1 and 2as was conducted on Examples 1 and 2.

Table 1 shows results of the tensile tests conducted on Examples 1 and 2and Comparative Examples 1 and 2. Table 2 shows evaluation results ofthe drawing formability, the piercing strength and the impact strengthobserved in each of Examples 1 and 2 and Comparative Examples 1 and 2.

TABLE 1 Rupture Elongation Ratio (%) Stress Ratio A Rupture Strength[MPa] Ratio Ratio Ratio Thickness 45 135 max/ 45 135 Amax/ 45 135 max/[μm] MD TD degrees degrees min MD TD degrees degrees Amin MD TD degreesdegrees min Example 1 15 141 114 133 130 1.24 2.5 3.38 2.64 2.86 1.35251 283 267 278 1.13 Example 2 25 155 109 137 120 1.42 2.11 3.77 2.652.82 1.79 265 299 284 262 1.14 Comparative 15 87.5 79.4 79.4 98.5 1.242.8 2.89 4.21 1.9 2.2 228 225 342 170 2.01 Example 1 Comparative 15 12766.9 78 112 1.9 1.55 5.13 4.13 1.9 3.31 210 346 316 223 1.65 Example 2

TABLE 2 Drawing Piercing Impact Strength [kg/cm] Formability Strength 23degrees C. Example 1 B 10 12.5 Example 2 B 15.4 Not Break※ Comparative D9.5 8.1 Example 1 Comparative D 9.5 10 Example 2 ※The film was notruptured although measured as in Example 1.[Evaluation Result]

As shown in Table 1, the ONy film 18 according to Examples 1 and 2 isexcellent in each of the deep-drawing formability, the piercing strengthand the impact strength as compared with Comparative Examples 1 and 2.

On the other hand, since Comparative Examples do not satisfy theabove-described conditions, there are problems with properties of theONy film 18 according to each of Comparative Examples.

Specifically, according to Comparative Example 1, the stress ratio A inthe 135 degrees direction is less than 2, the ratio (A_(max)/A_(min)) ofthe stress ratio A is more than 2, and the rupture strength in the 135degrees direction is less than 180 MPa. Thus, the film according toComparative Example 1 exhibits an inferior drawing formability, arelatively low piercing strength and an inferior impact strength.

On the other hand, according to Comparative Example 2, the ruptureelongation ratio in the TD direction is less than 70 percent, the stressratios A in the MD and 135 degrees directions are less than 2, and theratio (A_(max)/A_(min)) of the stress ratio A is more than 2. Thus, thefilm according to Comparative Example 2 exhibits an inferior drawingformability and a relatively low piercing strength.

Examples of Second Embodiment

Next, the second embodiment will be described in detail by reference toexamples and comparative examples.

In the examples of the second embodiment, what has been alreadydescribed in the examples of the preceding embodiment will not berepeated.

Examples 3 to 5 Manufacturing of Oriented Film

an extrusion of Ny6 pellets and an orientation of film were performed asin Examples 1 and 2.

Subsequently, the oriented film was put into a tenter heat treat furnace(not shown) and heat-fixed at 195 degrees C., whereby ONy film 18(hereinafter, also referred to as ONy film 18) according to Example 3was obtained. A crystallinity degree of the film according to Example 3was 33 percent and the film thickness was 15 μm.

ONy film 18 according to Example 4 was manufactured under the sameconditions as in Example 3 except that the oriented film was heat-fixedat 160 degrees C. by the tenter test treat furnace. A crystallinitydegree of the film according to Example 4 was 21 percent and the filmthickness was 15 μm.

ONy film 18 according to Example 5 was manufactured in substantially thesame conditions as in Example 3. A thickness of the ONy film 18 was 25μm and a crystallinity degree of the ONy film 18 was 33 percent.

[Evaluation Method]

A tensile test and evaluation methods of a drawing formability and apiercing strength in the present embodiment were the same as in thefirst embodiment, a description of which is omitted.

(Impact Strength)

A measurement of an impact strength was conducted with the film impacttester (manufactured by Toyo Seiki Seisaku-sho, Ltd.) by: striking fixedONy film 18 of a ring shape with the semispherical pendulum (diameter of½ inch); and measuring an impact strength (kg/cm) required for punchingthe film. Incidentally, the impact strength is represented in absolutevalue. The larger the value is, the more excellent impact resistance ofthe film is evaluated to be.

Comparative Example 3

ONy film 18 according to Comparative Example 3 was manufactured underthe same conditions as in Example 3 except that the oriented film washeat-fixed at 210 degrees C. in the tenter heat treat furnace. Acrystallinity degree of the film according to Comparative Example 3 was41 percent and the film thickness was 15 μm.

Comparative Example 4

ONy film 18 according to Comparative Example 4 was manufactured underthe same conditions as in Example 3 except that the oriented film washeat-fixed at 210 degrees C. in the tenter heat treat furnace. Acrystallinity degree of the film according to Comparative Example 4 was40 percent and the film thickness was 15 μm.

Comparative Example 5

ONy film 18 according to Comparative Example 5 was manufactured underthe same conditions as in Example 5 except that the oriented film washeat-fixed at 210 degrees C. in the tenter heat treat furnace. Acrystallinity degree of the film according to Comparative Example 5 was41 percent and the film thickness was 25 μm.

The same evaluation test was conducted on Comparative Examples 3 to 5 aswas conducted on Examples 3 to 5.

Table 3 shows the heat-treating temperature, the crystallinity degree, ahydrothermal shrinkage factor (a hydrothermal shrinkage factor of thefilm in the MD and TD directions when the film was retained in hotliquid of 95 degrees C. for thirty minutes) and the film thicknessrespectively in Examples 3 to 5 and Comparative Examples 3 to 5. Table 4shows results of the tensile tests conducted on Examples 3 to 5 andComparative Examples 3 to 5. Table 5 shows evaluation results of thedrawing formability, the piercing strength and the impact strength (23degrees C., −10 degrees C. and −30 degrees C.) observed in each ofExamples 3 to 5 and Comparative Examples 3 to 5.

TABLE 3 Heat-Treating Crystallinity Hydrothermal Temperature DegreeShrinkage Thickness [° C.] [%] Factor [%] [μm] Example 3 195 33 5 15Example 4 160 21 19 15 Example 5 195 33 5 25 Comparative 210 41 2 15Example 3 Comparative 210 40 2 15 Example 4 Comparative 210 41 2 25Example 5

TABLE 4 Rupture Strength [MPa] Rupture Elongation Ratio (%) Stress RatioA Ratio 45 135 Ratio 45 135 Ratio 45 135 max/ MD TD degrees degreesmax/min MD TD degrees degrees Amax/Amin MD TD degrees degrees minExample 3 114 102 123 97 1.27 2.67 3.00 3.44 2.94 1.29 297 333 312 3131.12 Example 4 109 81 98 99 1.35 2.83 4.53 3.87 3.29 1.60 306 360 351338 1.18 Example 5 123 93 114 103 1.32 2.67 3.00 3.44 2.94 1.29 297 338348 307 1.17 Comparative 87.5 79.4 79.4 98.5 1.24 2.80 2.89 4.21 1.902.20 228 225 342 170 2.01 Example 3 Comparative 141 114 133 130 1.242.50 3.38 2.64 2.86 1.35 251 283 267 278 1.13 Example 4 Comparative 102114 159 65 2.45 3.07 2.48 1.76 5.43 3.19 269 274 240 364 1.39 Example 5

TABLE 5 Piercing Impact Strength [kg/cm] Drawing Strength minus minusFormability [N] 23° C. 10° C. 30° C. Example 3 A 11.7 13.5 11.5 10.2Example 4 A 12 14.2 12.5 11.4 Example 5 A 17.4 Not Break※ 16.5 17.8Comparative D 9.5  8.1 6.5 5.8 Example 3 Comparative C 10 12.5 10.2 7Example 4 Comparative D 15.1 12.7 11 11.9 Example 5 ※“Not Break” meansthe film was strong enough to withstand a rupture.[Evaluation Result]

As shown in Table 3, the ONy film 18 according to each of Examples 3 to5 is excellent in each of the drawing formability, the piercing strengthand the impact strength as compared with Comparative Examples 3 to 5.

On the other hand, since Comparative Examples do not satisfy theabove-described conditions, there are problems with properties of theONy film 18 according to each of Comparative Examples.

Specifically, according to Comparative Example 3, the crystallinitydegree is less than 20 percent, the stress ratio A in the 135 degreesdirection is less than 2, the ratio (A_(max)/A_(min)) of the stressratio A is more than 2, and the rupture strength in the 135 degreesdirection is less than 180 MPa. Thus, the film according to ComparativeExample 3 has an inferior drawing formability, a relatively low piercingstrength and an inferior impact strength.

According to Comparative Example 4, since the crystallinity degree isless than 20 percent, the film according to Comparative Example 4 has aninferior drawing formability.

According to Comparative Example 5, the rupture elongation ratio in the135 degrees direction is less than 70 percent, the value obtained bydividing the maximum elongation ratio by the minimum elongation ratioout of the elongation ratios in the four directions is more than 2, thestress ratio A in 45 degrees is less than 2 and the ratio(A_(max)/A_(min)) of the stress ratio A is more than 2. Thus, the filmaccording to Comparative Example 5 has an inferior drawing formability.

Examples of Third Embodiment

Next, the Third embodiment will be described in detail by reference toexamples and comparative examples.

In the examples of the third embodiment, what has been already describedin the examples of the preceding embodiments will not be repeated.

Examples 6, 7 Manufacturing of Oriented Film

A mixture of Ny6 pellets and MXD6 pellets in which the pellets weremixed by a ratio of 70 parts by mass (Ny6) to 30 parts by mass (MXD6)was added with a thermal hysteresis material in a form of pellets by aratio of 10 percent by mass of the total amount of the film formingmaterial. In the thermal hysteresis material, the Ny6 and the MXD6 hadbeen once melt-mixed by the aforesaid ratio of 70 parts by mass (Ny6) to30 parts by mass (MXD6). After the dry-blended material was melt-kneadedin an extruder at 270 degrees C., a molten material was extruded from adie in a shape of cylindrical film. The extruded molten material wassubsequently quenched by water, whereby a raw film was obtained.

A melt point of the MXD6 was measured with a differential scanningcalorimetry (DSC) (manufactured by PerkinElmer Corporation) by raising atemperature from 50 degrees C. to 280 degrees C. at a speed of 10degrees C. per minute. In each of Examples, a value of the first run wasemployed as the melt point.

As the Ny6, nylon 6 (manufactured by Ube Industries, Ltd. [UBE nylon1023FD (trade name), relative viscosity: ηr=3.6]) was used. As the MXD6,metaxylylene adipamide (manufactured by Mitsubishi Gas Chemical Company,INC., [MX nylon 6007 (trade mark), relative viscosity ηr=2.7]) was used.

As the thermal hysteresis material, a material that had been extruded at270 degrees C. using a 40φ EX single screw (manufactured by YamaguchiManufacture Works, LTD.) was used, the material containing the Ny6 andthe MXD6 by the mixing ratio of 70 parts by mass to 30 parts by mass.

Then, as shown in FIG. 2, after inserted between the pair of nip rollers12, the raw film 11 was heated by the heater 13 while a gas was injectedinto the raw film 11. The raw film 11 was applied with the air 15 fromthe air ring 14 at the drawing start point to be distended to form thebubble 16. By pulling the raw film 11 using the pair of nip rollers 17provided at the downstream side, the simultaneous biaxial orienting inthe MD direction and the TD direction according to the tubular methodwas performed. The oriented ratios at the time of the orienting wererespectively 3.0 times (in the MD direction) and 3.2 times (in the TDdirection).

Subsequently, the oriented film was put into a tenter heat treat furnace(not shown) and heat-fixed at 200 degrees C., whereby ONy film 18(hereinafter, also referred to as ONy film 18) according to Example 6was obtained, the ONy film 18 having a thickness of 15 μm and ahydrothermal shrinkage factor of 3.4 percent.

ONy film 18 according to Example 7 was manufactured under the sameconditions as in Example 6 except that the thermal hysteresis materialwas added by 20 percent by mass of the total amount of the film formingmaterial and that the oriented film was heat-fixed in the tenter heattreat furnace at 160 degrees C. A crystallinity degree of the filmaccording to Example 7 was 19 percent and the film thickness was 15 μm.

[Evaluation Method]

A tensile test and an evaluation method of a drawing formability in thepresent embodiment were the same as in the first embodiment, adescription of which is omitted.

(Inner Separation)

A laminated packing material was prepared in a manner as described inthe section of the evaluation method of the drawing formability. Stripespecimens of 15 mm width were cut off from the laminated packingmaterial. Each end thereof was boundary-separated by hands by severalcentimeters, such that a front base material film (ONy film 18) and asealant film were separated. Subsequently, the film specimens each wereset in a tension tester (Instron Universal Tester, Type: 1123) toexperience a separation test for laminated portions at a speed of 300 mmper minute (90 degrees separation).

Since a peel-strength is dramatically degraded when an intra-layerseparation occurs inside the front base material film during theseparation test, the occurrence of the intra-layer separation can bedetermined by observing whether or not such a behavior is present. Forexample, when the peel-strength radically decreases from approximately 7N/m (value when the separation test is started) to approximately 1 to 2N/m in the middle of the separation test, an occurrence of anintra-layer separation can be determined.

Then, film that had showed no behavior of intra-layer separation insidethe front base material film was rated as “B” while film that had showeda behavior of intra-layer separation was rated as “D”.

(Seal Resistance)

A laminated packing material was prepared in a manner as described inthe section of the evaluation method of the drawing formability. Thelaminated packing material was seal-treated. The seal-treatment wasconducted under the following conditions: a temperature of a seal barwas 200 degrees C.; a seal with was 5 mm (no Teflon (RegisteredTrademark) tape was attached); a sealing time was 10 seconds; and apressure by the seal bar was 2 kg/cm². In evaluating the seal resistanceof laminated packing materials, laminated materials that had not adheredto the seal bar when seal-treated under the above-described conditionswere rated as “B”, laminated materials that had adhered to the seal barat that time were rated as “C”, and laminated materials that had adheredto the seal bar to experience an appearance whitening at that time wererated as “D”.

Comparative Example 6

ONy film 18 according to Comparative Example 6 was manufactured underthe same conditions as in Example 6 except that thermal hysteresismaterial was contained by 15 percent by mass of the total amount of thefilm forming material and that the oriented film was heat-fixed at 210degrees C. in the tenter heat treat furnace. A hydrothermal shrinkagefactor of the film according to Comparative Example 6 was 2.8 percentand the film thickness was 15 μm.

Comparative Example 7

ONy film 18 according to Comparative Example 7 was manufactured underthe same conditions as in Example 6 except that only Ny6 was used in thefilm forming material and that the oriented film was heat-fixed at 195degrees C. in the tenter heat treat furnace. A hydrothermal shrinkagefactor of the film according to Example 7 was 5 percent and the filmthickness was 15 μm.

The same evaluation test was conducted on Comparative Examples 6 and 7as was conducted on Examples 6 and 7.

Table 6 shows the film forming material, the content of the thermalhysteresis material, the heat-treating temperature and the hydrothermalshrinkage factor of Examples 6 and 7 and Comparative Examples 6 and 7.Table 7 shows results of the tensile tests conducted on Examples 6 and 7and Comparative Examples 6 and 7. Table 8 shows evaluation results ofthe drawing formability, the inner-separation and the seal resistanceobserved in each of Examples 6 to 7 and Comparative Examples 6 to 7.

TABLE 6 Material [% by mass] Thermal Hysteresis Heat-TreatingHydrothermal Thickness Ny6 MXD6 Material Content [% by mass] Temperature[° C.] Shrinkage Factor [%] [μm] Example 6 70 30 10 200 3.4 15 Example 770 30 20 160 19 15 Comparative 70 30 15 210 2.8 15 Example 6 Comparative100 0 0 195 5 15 Example 7

TABLE 7 Rupture Strength [MPa] Rupture Elongation Ratio (%) Stress RatioA Ratio 45 135 Ratio 45 135 Ratio 45 135 max/ MD TD degrees degreesmax/min MD TD degrees degrees Amax/Amin MD TD degrees degrees minExample 6 100 103 112 101 1.12 2.75 2.63 2.50 2.59 1.10 296 286 292 2951.04 Example 7 86 94 88 93 1.09 3.65 3.10 2.80 2.50 1.46 338 306 316 3261.10 Comparative 103 119 119 116 1.16 2.42 1.90 1.74 2.05 1.39 240 208236 223 1.15 Example 6 Comparative 114 102 123 97 1.27 2.67 3.00 3.442.94 1.29 297 333 312 313 1.12 Example 7

TABLE 8 Drawing Intra-Layer Seal Formability Separation ResistanceExample 6 A B B Example 7 A B B Comparative D B B Example 6 ComparativeA B D Example 7[Evaluation Result]

As shown in Table 6, the ONy film 18 according to Examples 6 and 7 isexcellent in each of the drawing formability, the inner-separation andthe seal resistance as compared with Comparative Examples 6 to 7.

On the other hand, since Comparative Examples do not satisfy theabove-described conditions, there are problems with properties of theONy film 18 according to each of Comparative Examples. Specifically,according to Comparative Example 6, since the stress ratios in the TDand 45 degrees directions are less than 2 percent, the film according toComparative Example 6 is inferior in the drawing formability. The filmaccording to Comparative Example 7, which does not contain MXD6 in thefilm forming material, is inferior in the seal resistance.

The invention claimed is:
 1. A biaxially-oriented film consistingessentially of: a nylon film consisting essentially of nylon 6, whereinsaid film has an elongation ratio in each of the machine direction,transverse direction, a 45 degree direction and a 135 degree direction,until a film rupture is 70 percent or more, the elongation ratio beingmeasured in a tensile test, wherein the testing conditions include: asample width of 15 mm; a distance between gauge points of 50 mm; and atensile speed of 100 mm/min, and a stress ratio A (σ₁/σ₂) between atensile stress σ₁ and a tensile stress σ₂ in a stress-strain curveobtained in the tensile test of the film is 2 or more in each of themachine direction, transverse direction, a 45 degree direction and a 135degree direction, the tensile stress σ₁ being a value at a point wherethe elongation ratio becomes 50 percent while the tensile stress σ₂being a value at an yield point, wherein an oriented ratio in thetransverse direction is larger than the oriented ratio in the machinedirection, and wherein a crystallinity degree of the film is in a rangeof 20 to 38 percent.
 2. The biaxially-oriented nylon film according toclaim 1, wherein a ratio (A_(max)/A_(min)) between a maximum stressratio A_(max) and a minimum stress ratio A_(man) of the stress ratios Aobtained with respect to the machine direction, transverse direction, a45 degree direction and a 135 degree direction is 2 or less.
 3. Thebiaxially-oriented nylon film according to claim 1, wherein atensile-rupture strength of the film in each of the machine direction,transverse direction, a 45 degree direction and a 135 degree directionmeasured in the tensile test of the film is 180 MPa or more.
 4. Alaminated packing material, comprising the biaxially-oriented nylon filmaccording to claim
 1. 5. A method of manufacturing thebiaxially-oriented film according to claim 1, comprising:biaxially-orienting an unoriented raw film made from the nylon 6 under acondition where an oriented ratio of the film in each of a machinedirection and a transverse direction becomes 2.8 times or more to make abiaxially-oriented raw film; and heat-treating the raw film at atemperature between 160 and 200 degrees C. to form a biaxially-orientedfilm having a crystallinity degree in a range of 20 to 38 percent. 6.The biaxially-oriented film according to claim 1, wherein thecrystallinity degree is obtained by heat treating the biaxially-orientedfilm at a temperature of from 160 to 195° C.
 7. The biaxially-orientedfilm according to claim 1, having a crystallinity degree of from 21 to33%.
 8. The biaxially-oriented film according to claim 1, which consistsof nylon
 6. 9. A cold formed molded article obtained by colddeep-drawing the biaxially-oriented film according to claim
 1. 10. Abiaxially-oriented film consisting essentially of: a nylon filmconsisting essentially of nylon 2, wherein said film has an elongationratio in each of the machine direction, transverse direction, a 45degree direction and a 135 degree direction, until a film rupture is 70percent or more, the elongation ratio being measured in a tensile test,wherein the testing conditions include: a sample width of 15 mm; adistance between gauge points of 50 mm; and a tensile speed of 100mm/min, and a stress ratio A (σ₁/σ₂) between a tensile stress σ₁ and atensile stress σ₂ in a stress-strain curve obtained in the tensile testof the film is 2 or more in each of the machine direction, transversedirection, a 45 degree direction and a 135 degree direction, the tensilestress σ₁ being a value at a point where the elongation ratio becomes 50percent while the tensile stress σ₂ being a value at an yield point,wherein a crystallinity degree of the film is in a range of 20 to 38%.11. The biaxially-oriented nylon film according to claim 10, wherein aratio (A_(max)/A_(min)) between a maximum stress ratio A_(max) and aminimum stress ratio A_(min) of the stress ratios A obtained withrespect to the machine direction, transverse direction, a 45 degreedirection and a 135 degree direction is 2 or less.
 12. Thebiaxially-oriented nylon film according to claim 10, wherein atensile-rupture strength of the film in each of the machine direction,transverse direction, a 45 degree direction and a 135 degree directionmeasured in the tensile test of the film is 180 MPa or more.
 13. Alaminated packing material, comprising the biaxially-oriented nylon filmaccording to claim
 10. 14. The biaxially-oriented film according toclaim 10, wherein the crystallinity degree is obtained by heat treatingthe biaxially-oriented film at a temperature of from 160 to 195° C. 15.The biaxially-oriented film according to claim 10, having acrystallinity degree of from 21 to 33%.
 16. The biaxially-oriented filmaccording to claim 10, which consists of nylon
 6. 17. A cold formedmolded article obtained by cold deep-drawing the biaxially-oriented filmaccording to claim 10.